Executive functions predict the success of top-soccer players

While the importance of physical abilities and motor coordination is non-contested in sport, more focus has recently been turned toward cognitive processes important for different sports. However, this line of studies has often investigated sport specific cognitive traits, while few studies have focused on general cognitive traits. We explored if measures of general executive functions can predict the success of a soccer player. The present study used standardized neuropsychological assessment tools assessing players’ general executive functions including on-line multi-processing such as creativity, response inhibition, and cognitive flexibility. In a first cross-sectional part of the study we compared the results between High Division players (HD), Lower Division players (LD) and a standardized norm group. The result shows that both HD and LD players had significantly better measures of executive functions in comparison to the norm group for both men and women. Moreover, the HD players outperformed the LD players in these tests. In the second prospective part of the study, a partial correlation test showed a significant correlation between the result from the executive test and the numbers of goals and assists the players had scored two seasons later. The results from this study strongly suggest that results in cognitive function tests predict the success of ball sport players.

Transcript of "Executive functions predict the success of top-soccer players"

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Executive Functions Predict the Success of Top-SoccerPlayersTorbjorn Vestberg1,2, Roland Gustafson2, Liselotte Maurex1, Martin Ingvar1, Predrag Petrovic1* ¨ ¨ ¨1 Department of Clinical Neuroscience, Karolinska Institutet Stockholm, Stockholm, Sweden, 2 School of Law, Psychology and Social Work, Orebro University, Orebro,Sweden Abstract While the importance of physical abilities and motor coordination is non-contested in sport, more focus has recently been turned toward cognitive processes important for different sports. However, this line of studies has often investigated sport- specific cognitive traits, while few studies have focused on general cognitive traits. We explored if measures of general executive functions can predict the success of a soccer player. The present study used standardized neuropsychological assessment tools assessing players’ general executive functions including on-line multi-processing such as creativity, response inhibition, and cognitive flexibility. In a first cross-sectional part of the study we compared the results between High Division players (HD), Lower Division players (LD) and a standardized norm group. The result shows that both HD and LD players had significantly better measures of executive functions in comparison to the norm group for both men and women. Moreover, the HD players outperformed the LD players in these tests. In the second prospective part of the study, a partial correlation test showed a significant correlation between the result from the executive test and the numbers of goals and assists the players had scored two seasons later. The results from this study strongly suggest that results in cognitive function tests predict the success of ball sport players. Citation: Vestberg T, Gustafson R, Maurex L, Ingvar M, Petrovic P (2012) Executive Functions Predict the Success of Top-Soccer Players. PLoS ONE 7(4): e34731. doi:10.1371/journal.pone.0034731 ´ Editor: Antonio Verdejo Garcıa, University of Granada, Spain Received September 3, 2011; Accepted March 6, 2012; Published April 4, 2012 Copyright: ß 2012 Vestberg et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The authors have no support or funding to report. Competing Interests: The authors have declared that no competing interests exist. * E-mail: Predrag.Petrovic@ki.seIntroduction players in different sports or players in the same sport where other tests have been used. Thus, different studies are hard to compare Sport and Psychology have since the early 1920s been and it is hard to understand how skills transfer across differentconnected in a joint research area [1]. The focus for Sport types of sports [9]. This is of a general interest since it has beenPsychology has mainly been to understand and develop the shown that experts in different sports are able to transfer cognitiveperformances among athletes in areas like motivation, group skills between sports that make them more successful in the newdynamics and mental training [2]. Another line of studies has sport then novices [10,11].focused on talent identification, in order to predict the success of an Many required skills in team sports may be translated to generalathlete [3]. These studies have investigated how personality traits cognitive domains where test results from successful players can beor states correlate to successful sport behavior but no clear or compared to a population norm. A good team player could beconsistent relationship has been demonstrated [4]. Multivariate characterized by excellent spatial attention, divided attention,analyses on ball-sport players have also been performed with working memory and mentalizing capacity. He or she must bevariables like somatotype, body composition, body size, speed, able to quickly adapt, change strategy and inhibit responses. Manyendurance, performance measures, technical skill, anticipation, of these abilities are referred to as ‘‘game intelligence’’ in sportsanxiety and task and ego orientation [5]. However, as for [12]. In neuropsychology these are collectively referred to aspersonality traits, no clear correlations between these variables executive functions [13]. These dynamic cognitive top-downand sport success have been established. processes correlate with each other but less with general IQ [14]. Apart from physical skills and basic coordination, success in Surprisingly, the impact of general executive functions on theball-sports also depends on how information is processed given the capacity of a player is largely unknown [15]. One of few publishedcomplex and quickly changing contexts. In the last two decades a studies on general cognitive skills in sports shows that there is awide range of perceptual-cognitive skills have been studied in positive relationship between successful sport performances insport. This research has mainly focused on areas like visual young soccer players and their cognitive creativity in general [16].anticipation, pattern recognition, knowledge of situational prob- Another problem in most research focusing on sport andabilities, and strategic decision-making [6]. This line of research cognition is the cross-sectional approach and the involvement of ahas mostly studied sport-specific tasks [7,8] comparing experts sport specific situation that needs sport specific assessment toolswith novices and has contributed to the understanding of sport made particularly for that study. The cross-sectional approachspecific demands. A weakness in these studies is that expert and makes it difficult to establish any causal relation and the sportnovice players cannot be compared with a neutral standard, with PLoS ONE | www.plosone.org 1 April 2012 | Volume 7 | Issue 4 | e34731

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Executive Functions Predict the Sport Successspecific tools make it difficult and expensive to repeat the research Table 1. Descriptive table of the four included groups: Highin new studies. Division Males (HD-M), High Division Females (HD-F), Low In the present study we have explored the importance of general Division Males (LD-M), and Low Division Females (LD-F).executive functions when it comes to predicting a successfuloutcome of a soccer player using both a cross-sectional and aprospective component. The study was divided in two parts and Position - Forw/ Age - Mean age Higher Educationour approach was to use well-known neuropsychological assess- Group N Mid/Def (SD) - Mean years (SD)ment tools and assess the soccer players’ executive functions such HD-M 14 6/5/3 25,00 (4,87) 0.75 (1.11)as the chain of creativity, working memory, multi-tasking and HD-F 15 4/9/2 25,60 (3,60) 1.87 (1.42)inhibition. We chose the Design Fluency test from the D-KEFSexecutive test battery as our primary test since it does not have a LD-M 17 4/6/7 23,24 (3,05) 0.59 (1.33)verbal component but include a creativity/planning aspect that we LD-F 11 4/4/3 22,18 (5,53) 1.05 (1.43)believe is important in team sports [6]. In order to strengthen ourfindings we also used two other executive tests from the same test There was no significant difference in age between HD-M and LD-M (t(29) = 1.232; p = 0.223), or HD-F and LD-F (t(24) = 1.911; p = 0.068). Likewise,battery (Colour-word interference test and Trail making test). In the first there was no significant difference in higher education between HD-M and LD-part we compared the results between High Division players (HD), M (t(29) = 0.364; p = 0.72), between HD-F and LD-F (t(24) = 1.448; p = 0.16), orLower Division players (LD) and a standardized norm group. In between HD and LD players if the players were not divided by genderthe second part, two seasons later, we compared the test results (t(55) = 1.541; p = 0.129. doi:10.1371/journal.pone.0034731.t001with a well-known measure of success in soccer, namely thenumber of goal and assist - an objective measurement thatcharacterizes the capacity of a team and a player without average the players were participating in 70% of the games duringsubjective valuations. the last 2.5 years.Methods Materials The tests used were from the D-KEFS test battery of executiveEthics Statement functions where the scoring is normalized for age. The primary The study protocol, including the ethical aspects of the study, test used was Design Fluency (DF), a standardized test whichwas approved by the Student Review Board at the Psychological measures on-line multi-processing such as creativity, response ¨Department of Orebro University. The study was performed in inhibition, and cognitive flexibility [17,18] and thus simulates thefull compliance with the Declaration of Helsinki. All subjects were executive chain of decision making in a similar way as in a realgiven verbal and written information on the study and gave their sport situation. DF is a non-verbal psychomotor test in which theverbal and written informed consent to participate. participant uses the hand and a pen to combine all dots in a square with one line. The task is to find as many different combinations asParticipants possible of binding together the dots under time pressure (60 sec) The participants in the first (cross-sectional) part of the study and the participant is not allowed to use a solution twice. Theincluded 57 male (n = 31) and female (n = 26) players (Table 1). 14 participant needs to remember previous responses in an onlinemale and 15 female participants from the Swedish highest national working memory and update new rules accordingly (i.e. not repeatsoccer leagues (Allsvenskan) were included in the highest division previous combinations). He or she must use inhibition skills ingroup, HD (Mage = 25.3; SD: 4.2). 17 male participants playing in order not to repeat previous responses. The participant also needsthe Swedish 3rd national division (called Division 1) and 11 female to constantly use a scanning skill to find new solutions to fulfill theparticipants from Swedish 2nd national division were included in task. All three subtests of DF were used. As additional tests Colour-the lower division group, LD (Mage = 22.8; SD: 4.1). There was no word interference test (CWI), i.e. Stroop test, and Trail making test (TMT)significant difference in age or educational level between the were used in order to confirm the result from of the primary test.different groups (see Table 1). These tests also measure general executive functions, but from a The test group in the second (prospective) part of the study more verbal aspect and without the creativity or problem solvingincluded 25 of the male players (13 from HD and 12 from LD at abilities aspects important in DF. Therefore, they are not optimal in the present analysis but serve as a control to the main test.the time of testing) that had played at least one game in 1st or 2nddivision since no official points were registered for the femaleplayers or players in division 3. Procedure The participants for the HD group came from six teams of the All the participating teams were visited at their training facilitieshighest division in Sweden, Allsvenskan. These teams represent 20% from 7 June to 30 October 2007. The selected players were tested(=) to 25% (R) of the teams in their divisions. In the end of the in a 40 minutes standardized process and with the same testseason their average position in the final table was place nine (=) of leader.fourteen and place six (R) of twelve. The participants for the LDgroup came from five of the lower division teams. These teams Designrepresent 20% (=) to 17% (R) of the teams in their divisions. In the The players were tested on their executive functions (fall 2007).end of the season their average position in the final table was the Prospective data of goal and assist was used (January 2008 to Mayplace five (=) of fourteen and place five (R) of twelve. The coaches 2010) to study whether DF measured in 2007 could predict thefrom these teams were responsible to select the participants based outcome of a soccer player’s success.on how well the soccer capacity of the individual playerrepresented the team average level. The coaches were asked to Statistic analysisselect two forwards, two midfielders and two defenders from their A 2-way full factorial ANOVA with division and gender asteams and also asked not to select players where the probability factors, and scores on the executive test as dependent variablewas large of soon transferring to a higher or lower league. In were used. Importantly, DF was used as our main analysis, as it PLoS ONE | www.plosone.org 2 April 2012 | Volume 7 | Issue 4 | e34731

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Executive Functions Predict the Sport Successwas the only one of the D-KEFS tests containing factors we believeare important in soccer (fast creativity or problem solving abilities)and at the same time did not contain verbal aspect that may behighly affected by education/schooling (such as CWI and TMT).Thus, CWI and TMT are specifically used to strengthen the DFanalysis. In order to be sure that other variables such as age,position and education did not affect the result we also performedan additional ANCOVA-analysis with the factors: division, genderand position, and the covariates: educational level and age. Scoreson the DF test were treated as dependent variable. In the prospective part a partial correlation between DF andsquare root of the points (goals and assists) controlling for the orderin the team i.e. forward, mid-player or defender (given thedifferent probabilities of scoring points) defined as two dummyvariables, the proportion played in 2nd vs. 1st division (given that itis easier to score points in the 2nd division) and the age (given bothgeneral physical decline and possible cognitive decline specificallyin soccer) were used.ResultsCross-sectional tests DF. Using the sum of scaled scores male and female soccer-players in both HD and LD performed highly above the standard Figure 1. In Design Fluency (DF) the High Division (HD) playerspopulation in average on DF (Male HD: +1.93 SD, Female HD: had significantly better scores than the Low Division players+1.76 SD, Male LD: +1.02 SD, Female LD: +1.12 SD). Thus, (LD). This difference was observed for both men and women. Note that both HD and LD players have superior scores compared with theHD-players belong to the 5% best individuals in the population on standard population.this test. doi:10.1371/journal.pone.0034731.g001 The ANOVA-model indicated a significant effect on DF-scoresF(3, 53) = 4.99, p = 0.004. There was a significant effect of division Prospective test(HD: mean-score: 15.52, SD: 2.42; LD: mean score: 13.18, SD: In the prospective partial correlation test the DF result from2.14; F(1, 53) = 13.86; p,0.0005) but not of gender (F(1, 2007 was significantly correlated to the points (expressed as the53) = 0.03; p = 0.86) or any interaction effect (F(1, 53) = 0.44; square root of the points due to a skewed distribution) madep = 0.51) (Figure 1). The effect was still present when also position, January 2008 to May 2010, Correlation cf = 0.54; p = 0.006 (1-age and education-level were controlled for (ANCOVA-analysis tailed).F = 9.51; p = 0.004). No other effects were significant in theANCOVA-analysis. CWI. There was a trend for HD.LD in the CWI 1/2 (HD: Discussionmean-score: 11.62, SD: 1.57; LD: mean score: 10.86, SD: 1.94, This study shows that general executive functions are importantF(1, 53) = 2.76, p = 0.10) and CWI 3 (HD: mean-score :12.48, SD: in soccer and can even predict a future success in soccer players. In1.79; LD: mean-score: 11.68, SD: 1.81; F(1, 53) = 2.57, p = 0.12) our cross-sectional test on executive functions (including ourthat are less demanding in terms of response suppression and primary test, DF, and the two other control tests - CWI and TM)response shifts. The more demanding test of executive functions, we found that the soccer players in the HD group had significanti.e. CWI 4, showed a significant difference between HD and LD better results than soccer players in the LD group. Moreover, both(HD: mean-score: 12.17, SD: 1.98; LD: mean score: 10.79, SD: groups performed much better on the executive tests than the2.79; F(1, 53) = 4,28, p = .044). Thus, only when there was a larger general population. The findings were observed for both male andrequirement of executive functions there was a better performance female players. The results are in line with previous studies onin the highest league vs. the lower league in this test. specific sport skills that indicate that elite athletes compared with TMT. In the part of the TMT which is testing sub- sub-elite or novice has superior cognitive performance when itcomponents important for executive functions including visual comes to sport specific situations [8]. Here we have been able toscanning, number sequencing, letter sequencing, and motor speed extend this finding to general executive functions but also to(i.e. TM 2/3) the HD group showed a significantly better compare performance of both groups to a general population. Inperformance compared with the LD group (HD: mean-score: the prospective part of the study we showed that the DF predicted13.07, SD: 1.75; LD: mean score: 11.54, SD: 2.52; F(1, 53) = 6.73, future success measured in goals and assists, suggesting a causalp = 0.012). Importantly, the HD group had significantly higher role for executive functions for sport success in soccer.points than the LD group on the primary executive component, Executive functions are not a uniformly defined term buti.e. TMT 4 (HD: mean-score: 11.69, SD: 1.47; LD: mean score: generally used as a term to describe the cognitive processes that10.68, SD: 1.66; F(1, 53) = 4.6; p = 0.037). regulate thought and action, especially in non-routine situations Correlation. DF correlated significantly with CWI 1/2 [19]. Examples of these processes are problem solving, planning,(r = 0.364; p = 0.005), CWI 3 (r = 0.414; p = 0.001), CWI 4 sequencing, selective and sustained attention, inhibition, utilization(r = 0.428; p = 0.001), TM 2/3 (r = 0.382; p = 0.003), TM 4 of feedback, multi-tasking, cognitive flexibility and ability to deal(r = 0.339; p = 0.011). with novelty [20]. Different theoretical models are used to describe the executive functions. Relevant for this study are the supervisory PLoS ONE | www.plosone.org 3 April 2012 | Volume 7 | Issue 4 | e34731

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Executive Functions Predict the Sport Successattentional system (SAS) model [21] and the working memory Studies on situational probabilities show that elite soccer playersmodel of Baddeley [22], since they both emphasize the global are better than their sub-elite counterparts in predicting andcognitive control operations of executive functions. The SAS ranking the ‘‘best passing options’’ available [32]. Thus, theymodel suggests a regulatory mechanism divided into two anticipate future events more efficiently, but also use thisinteractive components, the contention scheduling and the information to seek and pick up new information, and usesupervisory attentional control. Contention scheduling monitors different search strategies in different contexts of the play [29].the routine and over-learned behaviors while supervisory atten- Similar studies in other ball sports [33] suggest that playerstional control is responsible for monitoring new data and what is evaluate the probability of each possible event that could occurnot yet routine. SAS has further been developed to the theory of and then use this information to maximize the efficiency ofmulti-tasking performance in everyday life [23]. The executive subsequent behavior. Research from basketball and field hockeyfunctions have also been described as a fundamental part of [34,35] also points out the importance of cognitive evaluation andworking memory as the central executive component [24] that elite players have better ability than sub-elite players when itinteracting with the phonological loop and visual spatial sketchpad comes to recall of other players’ position in a specific game[22]. New information will be on-line analyzed and compared situation. These studies are in line with the suggestion that expertwith earlier stored information to provide guidance to decision. players are superior in executive functions compared with noviceThe ability to use and update memory in order to predict future players. However, they cannot isolate specific executive functionsactions is a key aspect of the executive functions [25]. nor relate it to the general population. On a more theoretical level The development of the executive functions is considered to the suggestion that top-players are superior in general executivetake place progressively throughout childhood and the adolescence functions may change how the relation between cognition andfrom birth to 19 years of age [26,27]. It is possible that good sport success is conceptualized.players actually develop better executive functions, although these A possible shortcoming of the prospective part of this study isfunctions have been regarded as relatively stable through life [28]. that we used goals and assists as our measures of performanceExecutive functions are related to only some aspects of IQ [14], i.e. quality and achievement. Thereby, this analysis may miss otherwhile the ability to update information in working memory is factors that are not measured - for example how well did differentclosely correlated with IQ, inhibition and quickly switching individuals defend or organize the early game forward. We hopebetween different data show little or no relation to IQ. that we have been able to partially control for this as we controlled The executive functions are thus important in order to capture for position in our analyses. Nevertheless, goals and assists are easyand discriminate among information in decision-making, espe- to measure and undisputable. Thus, they are a good approxima-cially during time constraints. In ball-sports like soccer there are tion of performance quality if other factors are well controlled for.large amounts of information for the players to consider in everynew moment. The successful player must constantly assess the Investment in soccer players is a risky business where predictivesituation, compare it to past experiences, create new possibilities, tools are lacking. This study suggests that the precision in selectingmake quick decisions to action, but also quickly inhibit planned the future stars should include not only judgement of physicaldecisions. Thus, several core-features of executive functions such capacity, ball control and how well the player performs at present.as planning, sustained and divided attention, suppression of Our data suggest that measures of executive functions withprevious responses, and working memory capacity are important validated neuropsychological tests may establish if a player has thefor a team player in soccer. These executive functions are assessed capacity to reach top levels in soccer. Thus, the present study mayin the tests used in the present study. change the way ball-sports are viewed and analysed and how new Executive functions - as a part of specific task related talents are recruited.perceptual-cognitive functions - have previous been extensivelystudied in cognitive sports psychology for specific sports. For Author Contributionsexample it has been shown that expert soccer players can recall Conceived and designed the experiments: TV RG MI PP. Performed theand recognize patterns of play more effectively than inexperienced experiments: TV. Analyzed the data: TV RG LM MI PP. Contributedsoccer players [29] and that expert players in general have reagents/materials/analysis tools: TV RG LM MI PP. Wrote the paper:superior visual discrimination in a game-like situation [30,31]. TV RG LM MI PP.References1. Gould D, Pick S (1995) Sport psychology: The Griffith era, 1920–1940. The 11. Williams AM, Ford PR, Eccles DW, Ward P (2010) Perceptual-Conitive Sport psychologist, Special issue: Sport psychology: A Historical perspective 9: Expertise in Sport and its Acquisition: Implications for Applied Cognitive 391–405. Psychology. Wiley Online LibraryDOI 10.1002/acp.1710.2. Williams JM (2006) Applied Sport Psychology. New York: McGraw-Hill 12. Stratton G, Reilly T, Richardson D, Williams AM (2004) Youth soccer: From companies, Inc. science to performance. London: Routledge.3. 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